Nonarteritic anterior ischemic optic neuropathy is the most common type of ischemic optic neuropathy, a condition in which insufficient blood supply to the optic nerve damages it, resulting in loss of vision.  NAION mostly develops in adults over the age of 50.  It affects between 2.3 and 10.3 people per 100,000 individuals per year.  Patients with NAION will typically have some or all of the signs of an optic neuropathy including decreased visual acuity, dyschromatopsia, an RAPD, a swollen optic nerve with splinter hemorrhages, and a visual field defect.  Visual loss is usually sudden, or over a few days at most, and is usually permanent, with some recovery possibly occurring within the first weeks or months.

The diagnosis of NAION is based on the typical symptoms and signs.  While some rare causes of NAION are treatable, there is no effective treatment to reverse NAION in the vast majority of cases once it happens.

Mutations within the GP1BA gene, located on chromosome 17p13.2 have been associated with significant risk for NAION disease.  Also mutations within the mitochondrial Cytochrome c Oxidase III gene have been identified in patients with NAION disease.